(1) Technical Field of the Invention
This invention relates to small-sized and precision injection molding apparatus for producing small-volumed, small-sized and high precision molded articles.
(2) Description of the Prior Art
About 60% of conventional injection molding machines are provided with large-sized clamping devices each having more or less 150 tons. However, in connection with a remarkable progress of semiconductor technology, demand for small-sized and precision molded articles is increased rapidly in electronics industry. According to a statistics of the Ministry for International Trade and Industry, Japan in 1984, about 60% of the injection molding machines are occupied by small-sized machines each having less than 100 tons. Today, a main current of electronic devices such as computers, video devices, office automation machines and their peripheral devices is to make each device more compact and smaller and simultaneously make its accuracy higher. It is foreast that such a tendency will be expedited furthermore on a global level in the future.
Despite such strong desire of electronics industry, for the time being, a basic construction of conventional large-sized injection molding machine is hardly modified, in which each section of it is small-sized partially.
In recent small-sized injection molding machines, it becomes more difficult to make compact the construction of raw material supply means, raw material plasticization means, injection plunger means, melted resin flow means or the like, although the molded articles become more compact and smaller. In addition, since a conventional injection molding machine is employed, the disadvantage is that the melted resin injected by an injection plunger is inclined to retain in a long flow passage disposed in a mold for a relatively long time before the melted resin is injected in a cavity, thereby it may be changed in quality or solidified due to cooling.
Further, such a conventional injection molding machine adopts a sprue runner system in order to carry out a precision molding, so that it is unavoidable to expend costly materials wastefully, with the molding cost being increased. In view of the aforegoing, this invention has been attained.